Private LAN and NAT Configuration

I want to set up a private LAN with NAT Configuration. I have the following requirements:

1) One PC, which has two NICs (network adapters). Windows XP installed on one partition and Suse Linux on another. This PC should have access to the internet with its public IP address via one of the adapters(basically, this is a server) and another adapter to the Switch that holds other local clients. I want to configure a NAT on Linux to be my server.

2) One client Notebook that has only a private IP address therefore should not bound outside that local network. Windows XP (and Vista) is installed

3) One client PC that has only a private IP address therefore should not bound outside that local network. Windows XP installed

Basically I know how to assign local IP addresses within the address range: 192.168.1.X - on Windows systems. The problem is I don't know to configure the other adapter (*point (1)) such that only this machine should have access to the internet and as Linux Server for other client machines.

Please help me. I am a newby to all this and would appreciate a clearly layed out instruction.